In the case of the TestApp main() method you do not declare input anywhere, so the compiler complains about the line

Java Code:

n1 =input.nextInt();

Likewise you have undeclared variables in your minimum() and max() methods: minimum and maximum. You might find things less confusing if you make the method and variable names different, and keep the naimg consistent: so min()/max(), and minimum/maximum.

(Also when you post code, use the "code" tags: put [code] at the start of your code and [/code] at the end.)